Current technologies utilized for gaseous hydrogen storage are limited by the low volume storage gas density even at very high pressures such as in the range of from 5,000 to 10,000 psi. The energy density by volume of gaseous hydrogen is less than that of a gasoline energy density. Use of hydrogen as an alternate fuel source is limited due to this lower energy density. Cryogenic storage of hydrogen at temperatures of around 20 Kelvin may improve the volumetric energy density compared to gaseous storage but is still less than that for a given amount of energy compared to gasoline. Additionally, production of liquid hydrogen is energy intensive and requires special considerations due to the low temperature storage to avoid hydrogen boil off and other limitations of a liquefied hydrogen fuel source.
Chemical storage of hydrogen in a solid material including metal hydrides allows for hydrogen release when heated or mixed with water. However, formation of solid byproducts as well as the release of hydrogen at very high temperatures, sometimes even exceeding the melting point of a metal hydride material, limits the use of such materials. Additionally, metal hydride materials are typically not able to be rehydrated after hydrogen release.
There is therefore a need in the art for an improved hydrogen storage material that releases hydrogen at lower temperatures and is able to be rehydrated after release of the hydrogen so that onboard storage becomes feasible